1. Field of the Invention
This invention relates in general to thread gaging devices, and in particular to a device that uses three gage rollers spaced 120 degrees apart from each other and adjustable to various thread diameters.
2. Description of the Prior Art
Threads on screws and bolts are often gaged for quality assurance. One type of thread gaging device utilizes three gage rollers. Each roller has threads which have been formed to specification. The rollers are rotatably mounted on a device 120 degrees apart from each other. One of the rollers can be pivoted back to allow a threaded member to be inserted. Then a measuring device will measure the deflection of the pivotal member to determine whether or not the threads have been accurately formed.
While this is workable for threads of a particular diameter and pitch, if the device is to be used for measuring the diameters of more than one pitch, adjustments must be made. In the prior devices, typically the rollers will slide on slides which extend outward on radial lines from a center line located equidistant between the three gage rollers. A template can be placed over the rollers to determine the desired position relative to each other. Then the rollers will be fixed to the slides at that position.
A disadvantage of this type of device is that it is very difficult to precisely position rollers at the correct position, even with a template. Because all three of the rollers will slide on radial lines, it is possible for the template to fit over the gage rollers in more than one position relative to the base of the thread gage. The gage rollers could be slightly cocked with the center line of the template off from the true center line of the device. This would affect the measurement.